We use knockout at work but

    <p data-bind="if: foo">foo!</p>

quickly turns into

    <!-- ko if: foo -->
        <p>foo!</p>
        <p>
          because this also depends on foo and I should
          keep it DRY and adding a parent element just
          to contain that "if" is silly.
        </p>
    <!-- /ko -->

Then you start to get comments everywhere and sometimes they don't match and you write server-side helpers to contain them then it becomes a soup of html, your server side templating language and knockout annotations.

JSX is way cleaner.

We are still probably going to migrate to Vue.js though because it will be easier. (We love Knockout but having performance problems on edge cases.)